DE102010038295A1 - Method and device for sensorless position detection of an electronically commutated electrical machine - Google Patents

Abstract

The invention relates to a method for determining a rotor position of a rotary, multiphase, electronically commutated electrical machine (1), the electrical machine (1) having a plurality of phase windings (4) which can be energized via phase connections, with the following steps: - Determining phase voltages and phase currents at phase connections of the electrical machine (1); - Determining the induced voltages at the phase connections of the electrical machine (1) from the determined phase voltages and phase currents; - Providing the voltage pointer of the induced voltage determined by the induced voltages with respect to a stator-fixed Cartesian coordinate system; - Determining the rotor position as a space vector angle of the voltage pointer of the induced voltage provided with respect to the stator-fixed Cartesian coordinate system.

Description

Technical area

The present invention relates to electronically commutated electrical machines, in particular to methods for sensorless position detection of a rotor of an electrical machine.

State of the art

For the electronic commutation of brushless electrical machines information about the current rotor position is necessary. Using the rotor position, an electronic commutation is carried out by depending on the rotor position phase voltages applied to the electric machine or tapped when operated as a generator at this.

Various methods for determining the rotor position are known. In a group of electric machines, the rotor position is detected by an integrated or separate position sensor and provided to the control unit, which performs the electronic commutation. In another group of electrical machines, the rotor position is determined sensorless from the motor voltages and / or motor currents.

A known method for sensorless position detection is the so-called back-EMF method, in which a rotor position is derived from a profile of the induced voltage in a phase strand of the electrical machine. Since it is necessary for the measurement of the induced voltage to turn off the corresponding phase terminals without current, one is limited to the use of the back-EMF method in the choice of the suitable Bestromungsmuster for the electronic commutation.

Furthermore, a rotor position determination by means of the back-EMF method is usually exactly possible in such electrical machines, in which the induced voltage describes a sinusoidal course and the phase voltages are not provided by an inverter, since there can not be de-energized a phase connection. An example for the noise behavior advantageous permanent voltage specification (without blanking interval) is not possible with a back-EMF method. The quality of known methods for the sensorless operation of sinusoidal machines, for example in the case of a sensorless, closed-loop control, decreases the more the course of the induced voltage deviates from a sinusoidal profile.

It is therefore an object of the present invention to provide an improved method for the sensorless detection of the rotor position available, which can also be used when the induced voltages are not sinusoidal and which can be used regardless of the Kommutierungsart.

Disclosure of the invention

This object is achieved by the method for determining a rotor position of an electric machine according to claim 1 and by the device and the motor system according to the independent claims.

Further advantageous embodiments are specified in the dependent claims.

• – Bestimmen von Phasenspannungen und Phasenströmen an Phasenanschlüssen der elektrischen Maschine;
• – Ermitteln der induzierten Spannungen an den Phasenanschlüssen der elektrischen Maschine aus den bestimmten Phasenspannungen und Phasenströmen;
• – Bereitstellen des durch die induzierten Spannungen bestimmten Spannungszeiger der induzierten Spannung bezüglich eines statorfesten kartesischen Koordinatensystems; und
• – Bestimmen der Läuferlage als einen Raumzeigerwinkel des bezüglich des statorfesten kartesischen Koordinatensystem bereitgestellten Spannungszeigers der induzierten Spannung.

According to a first aspect, a method for determining a rotor position of a rotary, multi-phase, electronically commutated electric machine is provided. The electric machine has a plurality of phase windings, which can be energized via phase connections. The method comprises the following steps:

• Determining phase voltages and phase currents at phase terminals of the electrical machine;
• - detecting the induced voltages at the phase terminals of the electric machine from the determined phase voltages and phase currents;
• - Providing the determined by the induced voltages voltage vector of the induced voltage with respect to a stator-fixed Cartesian coordinate system; and
• Determining the rotor position as a space vector angle of the voltage vector provided with respect to the stator-fixed Cartesian coordinate system.

One idea of the above method is to determine the induced voltage in the phase windings in a multi-phase electric machine and to provide it as a voltage vector of a fixed-stator coordinate system, so that the space vector angle of the induced voltage is an indication of the rotor position or can be assigned directly. This allows a particularly simple derivation of the rotor position from the induced voltage.

In particular, the provision of the voltage vector of the induced voltage determined by the induced voltages with respect to the stator-fixed Cartesian coordinate system can be carried out by converting the determined induced voltages into the stator-fixed Cartesian coordinate system, or by the determined phase voltages and phase currents at the phase terminals of the electrical machine are converted into the stator-fixed Cartesian coordinate system before the induced voltages are determined therefrom.

Furthermore, the converted voltage vector of the induced voltage can be subjected to a correction angle, the correction angle depending on the voltage vector angle. In order to determine the rotor position from the induced voltage even with non-sinusoidal induced voltages, the correction angle is used to correct the error of a non-sinusoidal induced voltage in the rotor position determination.

According to one embodiment, the correction angle may be determined using the voltage vector angle and / or the rotor speed.

The correction angle can be determined using a lookup table by specifying the voltage vector angle and / or the speed.

According to a further embodiment, the determination of the phase voltages and phase currents at the phase terminals of the electric machine can be carried out by measuring the phase voltages and phase currents or by determining the phase voltages from a DC link voltage provided and a pulse width modulation duty cycle with which the phase connections are driven ,

• – eine Einrichtung zum Bestimmen von Phasenspannungen und Phasenströmen an Phasenanschlüssen der elektrischen Maschine;
• – eine Steuereinheit, die ausgebildet ist, um • die induzierten Spannungen an den Phasenanschlüssen der elektrischen Maschine zu ermitteln; • um den durch die induzierten Spannungen bestimmten Spannungszeiger der induzierten Spannung bezüglich eines statorfesten kartesischen Koordinatensystems bereitzustellen; und • um die Läuferlage als einen Spannungszeigerwinkel des bezüglich des statorfesten kartesischen Koordinatensystem bereitgestellten Spannungszeigers der induzierten Spannung zu bestimmen.

According to a further aspect, an apparatus for determining a rotor position of a rotary, multi-phase, electronically commutated electric machine is provided. The electric machine has a plurality of phase windings, which can be energized via phase connections. The device comprises

• A means for determining phase voltages and phase currents at phase terminals of the electric machine;
• A control unit configured to: detect the induced voltages at the phase terminals of the electric machine; • to provide the induced voltage voltage phasor of the induced voltage with respect to a stator-fixed Cartesian coordinate system; and • to determine the rotor position as a voltage phasor angle of the induced voltage voltage phasor provided with respect to the stator-fixed Cartesian coordinate system.

In another aspect, an engine system is provided with a rotary multi-phase electronically commutated electric machine and the above apparatus.

• – Empfangen von Angaben zu den Phasenspannungen und Phasenströmen an Phasenanschlüssen der elektrischen Maschine;
• – Ermitteln der induzierten Spannungen an den Phasenanschlüssen der elektrischen Maschine aus den empfangenen Phasenspannungen und Phasenströmen;
• – Bereitstellen der durch die induzierten Spannungen bestimmten Spannungszeiger der induzierten Spannung bezüglich eines statorfesten kartesischen Koordinatensystems; und
• – Bestimmen der Läuferlage als einen Spannungszeigerwinkel des bezüglich des statorfesten kartesischen Koordinatensystem bereitgestellten Spannungszeigers der induzierten Spannung.

According to a further aspect, there is provided a computer program product containing a program code which, when executed on a data processing unit, in the method according to one of claims 1 to 4, performs the following steps:

• - Receiving information about the phase voltages and phase currents at phase terminals of the electric machine;
• - detecting the induced voltages at the phase terminals of the electric machine from the received phase voltages and phase currents;
• - Providing the determined by the induced voltages voltage vector of the induced voltage with respect to a stator-fixed Cartesian coordinate system; and
• Determining the rotor position as a voltage vector angle of the induced voltage voltage vector provided with respect to the stator-fixed Cartesian coordinate system.

Brief description of the drawings

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

1a a schematic representation of a synchronous machine as an example of an electronically commutated electric machine;

1b an auxiliary representation for illustrating a conversion of the voltage vector of the induced voltage in a stator fixed Cartesian coordinate system; and

2 a flowchart for illustrating the method for determining the rotor position from the induced phase voltage.

Description of embodiments

In 1 is a simplified representation of a three-phase electronically commutated electrical machine 1 shown as an internal rotor machine. One recognizes a stature 2 with three offset by 120 ° to each other stator teeth 3 , In practice, the number of stator teeth 3 on the stator 2 usually larger and corresponds for example to a multiple of three, such. For example, nine, twelve or eighteen.

The stator teeth 3 are each with a phase winding 4 provide and provide corresponding energizing a component of the stator magnetic field available. The stator windings 4 are connected in a conventional manner in delta connection or in star connection with each other. Each of the stator windings 4 can via a corresponding phase connection (not shown) of the electric machine 1 be energized.

Inside the stator 2 is rotatably a rotor 5 as a runner of the electric machine 1 attached, which in the simplified representation of the 1a two rotor poles 6 has, which are arranged opposite to each other. In practice, synchronous machines may have more than two rotor poles, for example four or eight rotor poles.

It is a control unit 10 provided, the z. B. using a driver circuit 11 the stator windings 4 controls. The control takes place by means of an electronic commutation, so that each of the phase windings 4 depending on the position of the rotor 5 is applied with a phase voltage. Through the control unit 10 For example, various types of commutation may be provided, such as block commutation or trapezoidal commutation, and the like. In addition to the electronic commutation, a specific phase voltage can be generated by a pulse width modulation of an applied intermediate circuit voltage or supply voltage.

To detect the induced voltage, it has hitherto been necessary to provide a phase connection of the electrical machine 1 to de-energize and to determine and evaluate the applied there, induced in the associated phase winding voltage. This is usually done in specified blanking intervals whose duration is limited to the least possible impact on the control of the electrical machine 1 exercise.

Alternatively, the induced voltage can also be determined by determining the phase voltages Ŭ _S and the phase currents ĭ _{S at} the phase terminals. The phase voltages Ŭ _S and the phase currents ĭ _S can be determined, for example, by measurement. The measurement of the phase voltages Ŭ _S and the phase currents ĭ _S is performed by suitable measuring devices 12 that are either in the driver circuit 11 or in the control unit 10 can be provided. The measuring devices 12 For example, they may include shunts, analog-to-digital converters and the like. Alternatively, the phase voltages Ŭ _S and the phase currents ĭ _{S may be obtained} from a measurement or knowledge of one at the driver circuit 11 applied DC link voltage (supply voltage) and the duty cycle of the pulse width modulation, with which the relevant phase winding is controlled, are determined.

From the phase voltages Ŭ _S and the phase currents Ĭ _S , the induced voltage Ŭ _{ind is} determined accordingly. In vector notation:

It has proven to be particularly advantageous to represent the induced voltage Ŭ _ind as a circulating voltage vector of a stator-fixed coordinate system, in particular of a Cartesian coordinate system. This is schematically in 1b shown, wherein as a substitute image of the stator 2 two staggered by 90 ° stator windings 4 having. Using the two spare stator windings 4 , which is offset by 90 ° to each other on the stator 2 are arranged, it is clarified that the stator windings 4 in a multi-phase electric machine, as exemplified in 1a is shown, can always be displayed in a statorfesten coordinate system, ie on an electric machine with mutually offset by 90 ° stator windings. In the above example, from the indications of the induced voltages U _ind1 , U _ind2 , U _ind3 in the three-phase system, the induced voltage of the stator-fixed Cartesian coordinate system in polar representation can be determined as follows: Ŭ _ind = U _ind · e ^-jφ = U _ind1 · e ^{-j0 °} + U _ind2 · e ^{-j120 °} + U _ind3 · e ^{-j240 °}

The space vector angle φ of the induced voltage determined according to the above formula then directly represents the rotor position of the rotor 5 represents.

The prerequisite for this is that the induced voltage Ŭ _{ind has} a sinusoidal course. The induced stress Ŭ _ind is to a considerable extent dependent on the construction of the electric machine, in particular on the shaping of the air gap between the rotor poles 6 and the stator teeth 3 , In order to determine the actual rotor position φ ', therefore, a correction must be carried out at a non-sinusoidal induced voltage. For this purpose, for example, a correction angle K (φ) dependent on the space vector angle can be provided, with which the space vector angle is applied to the non-sinusoidal induced voltage Ŭ _{ind in} order to correct it to the rotor position. The result of the correction is that the space vector angle φ of the non-sinusoidal voltage is also dependent on the correction angle K (φ) as a function of the position.

In addition to the space vector angle φ, the rotational speed n of the electrical machine can be taken into account, since the induced voltage Ŭ _ind, in particular its course, is likewise dependent on the rotational speed n. The provision of the correction angle K (φ, n) is generally carried out by a look-up table, which is either after the production of the electrical machine 1 is taught-in individually for the individual engine or specified depending on the engine type.

The speed n can be determined in various ways. According to a first possibility, the rotational speed n can be determined as the derivative of the rotor position φ '. However, there is a disadvantage in that there is a feedback in the calculation because φ '= φ + K (φ, n). Under certain circumstances, this can lead to oscillation of the indication of the rotational speed n.

Alternatively, the speed n as a quotient n = | U _ind | / | Km (φ 'or φ) | where Km corresponds to the attitude constant dependent motor constant.

According to a further improvement, the rotational speed n can be determined as follows: n = | U _ind | / | Km '| where Km 'corresponds to a filtered Km (φ' or φ). On Km (φ 'or φ), the same filter is applied to it, with which also U _ind is acted upon by its determination. The filter that U _ind experiences results, for example, from the type of measurement (eg digital sampling) and determination of U _ind . By deriving the phase current to dt, a low-pass filtering is effected, for example, by the finite dt.

The learning can be done, for example, by the phase potentials for certain rotor positions φ 'and speeds n in the currentless case, ie at non-applied phase voltages, and thus a course of the induced voltage Ŭ _ind depending on the rotor position φ' and the rotational speed n are detected can. The correction angle K (φ, n) results from the difference between the rotor position φ ' _mess and the space vector _{angle of} the determined induced voltage Ŭ _{ind_mess} at a certain rotor position φ' _mess and a certain speed n _mess .

In 2 is a flowchart illustrating the method for determining the rotor position of an electric machine 1 shown. In step S1, first the induced voltages at the phase terminals across which the phase windings 4 be energized determined. For this purpose, the applied phase voltages and the corresponding phase currents are detected and the induced voltages are determined according to the above formula. From this, the induced voltage at the corresponding phase connection is determined.

In step S2, the thus determined induced voltages for each phase are converted into a stator-fixed Cartesian coordinate system and one obtains an amount of the induced voltage and a space vector angle for the current rotor position.

In step S3, the space vector ^angle φ of the induced voltage U _ind · e ^{-jωφ is} applied (added) to the corresponding correction ^angle K (φ, n), which is determined from a look-up table or according to a predetermined function.

The corrected space vector angle φ ' φ '= φ + K (φ, n) is calculated in step S4. The corrected space vector angle φ 'corresponds to the rotor position or the rotor position can be derived therefrom with a simple offset.

Claims (9)

Method for determining a rotor position of a rotary, polyphase, electronically commutated electric machine ( 1 ), wherein the electric machine ( 1 ) several phase windings ( 4 ), which can be energized via phase connections, with the following steps: determining phase voltages and phase currents at phase connections of the electrical machine ( 1 ); Determining the induced voltages at the phase terminals of the electrical machine ( 1 ) from the determined phase voltages and phase currents; - Providing the determined by the induced voltages voltage vector of the induced voltage with respect to a stator-fixed Cartesian coordinate system; Determining the rotor position as a space vector angle of the voltage vector provided with respect to the stator-fixed Cartesian coordinate system. The method of claim 1, wherein providing the induced voltage voltage phasor determined by the induced voltages with respect to the fixed magnetic coordinate system is performed by converting the detected induced voltages into the stator-fixed Cartesian coordinate system, or by determining the determined phase voltages and phase currents at the phase terminals electric machine ( 1 ) are converted into the stator-fixed Cartesian coordinate system, before the induced voltages are determined from these. The method of claim 1 or 2, wherein the space vector angle of the converted voltage vector of the induced voltage is applied to a correction angle, wherein the correction angle depends on the voltage vector angle. Method according to one of claims 1 to 3, wherein the correction angle using the voltage vector angle and / or using the speed of the rotor is determined. Method according to one of the preceding claims, wherein the correction angle is determined by means of a look-up table by specifying the voltage vector angle and / or the rotational speed. Method according to one of claims 1 to 5, wherein determining the phase voltages and phase currents at the phase terminals of the electrical machine ( 1 ) is performed by measuring the phase voltages and phase currents, or by detecting the phase voltages from a provided intermediate circuit voltage and a duty cycle of a pulse width modulation with which the phase connections are driven. Device for determining a rotor position of a rotary, polyphase, electronically commutated electric machine ( 1 ), wherein the electric machine ( 1 ) has a plurality of phase windings, which can be energized via phase connections, comprising: a device for determining phase voltages and phase currents at phase connections of the electric machine ( 1 ); A control unit which is designed in order to control the induced voltages at the phase connections of the electrical machine ( 1 ) to investigate; • to provide the voltage vector of the induced voltage determined by the induced voltages with respect to a stator-fixed Cartesian coordinate system; and • to determine the rotor position as a voltage vector angle of the induced voltage voltage vector provided with respect to the stator-fixed Cartesian coordinate system. Motor system with a rotary, polyphase, electronically commutated electric machine ( 1 ) and with the device according to claim 7. A computer program product containing program code which, when executed on a data processing unit, in the method of any one of claims 1 to 6, performs the steps of: - receiving information about the phase voltages and phase currents at phase terminals of the electric machine ( 1 ); Determining the induced voltages at the phase terminals of the electrical machine ( 1 ) from the received phase voltages and phase currents; - Providing the determined by the induced voltages voltage vector of the induced voltage with respect to a stator-fixed Cartesian coordinate system; and determining the rotor position as a voltage vector angle of the converted voltage vector of the induced voltage.

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